Anatomical causes of abdominal wall herniation

Anatomical causes of abdominal wall herniation

These may be classified as areas of natural weakness due to absence of muscle, natural defects that allow structures to enter or leave the abdomen, developmental abnormalities and disruptions of the abdominal wall as a result of injury . The only natural weaknesses caused by inadequate muscular strength are the lumbar triangles (see Lumbar hernia the posterior wall of the inguinal canal ( Figure 64.3 ). Many structures enter and leave the abdominal cavity , cre ating weakness that can lead to hernia formation. The most common example is the inguinal canal, along which, in males, the testis and its associated vessels descend from the abdomen to scrotum a t the time of birth. In females the round ligament traverses the inguinal canal. The resultant weakness may lead to an indirect inguinal hernia. The risk of inguinal hernia is related to the anatomical shape of the pelvis and is greater in Giovanni Battista Morgagni , 1682–1771, Professor of Anatomy , Padua, Italy . Vincent Alexander Bochdalek , 1801–1883, Professor of Anatomy , Prague, Czech Republic. inherent areas of weakness include the oesophageal hiatus, the femoral canal and the umbilical cicatrix. Failure of normal development may lead to congenital her - nias. The most common is an indirect inguinal hernia arising through failure of the processus vaginalis to close. As the testis (or round ligament) descends, it pulls a tube of peritoneum along with it. This tube should naturally fibrose and become obliterated, but, if it fails to do so , a hernia may develop. Recent studies have shown that calcitonin gene-related pep - tide and hepatocyte growth factor influence the closure of the processus, raising the possibility of a hormonal cause of hernia development. Other examples of congenital herniation include Morgagni and Bochdalek hernias of the diaphragm and some umbilical her nias. In neonates these are often seen in association with other congenital abnormalities. Weak areas of the abdominal wall may also arise from direct injury . A surgical scar, even with perfect wound heal - ing, has only 70% of the initial muscle strength, resulting in incisional herniation in at least 10% of laparotomy incisions. Smaller laparoscopic port-site incisions have a hernia rate of 1%. Increasing use of the laparoscopic surgical appr oach should lead to a fall in the incidence of incisional hernia. Muscle damage by blunt trauma or tearing of the abdom - ) and inal muscles is rare but is seen after exceptional force, such as high-speed motor vehicle accidents ( Figure 64.4 ). - Summary box 64.1 Causes of hernia /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

Figure 64.3 A right direct inguinal hernia defect (yellow arrows) is above the inguinal ligament (arrowheads). The round ligament (green arrow) enters the deep inguinal ring just lateral to the inferior epigastric vessels (black arrow). Anatomical weakness Developmental failures Genetic weakness of collagen Sharp and blunt trauma Weakness due to ageing and pregnancy Primary neurological and muscle diseases Figure 64.4 Traumatic hernia in the right iliac fossa (arrow) following a motor vehicle accident in which the lateral muscles, along with a tiny sliver of bone, were torn off the iliac crest.

A normal abdominal wall has su ffi cient strength to resist high abdominal pressure and prevent herniation of content. Many patients will first notice a hernia after excessive straining, the strain bringing the hernia to the attention of the patient, rather than being the cause. There is good evidence that hernia is a ‘collagen disease’ and is due to an inherited imbalance in the types of collagen. This is supported by histological evidence and relationships between hernia and other diseases related to collagen, suc as aortic aneurysm. In extreme collagen disorders, such as Ehlers–Danlos syndrome, successful long-term repair of a her nia can be very di ffi cult. Hernia is more common in smokers as smoking is linked to impaired collagen maturation. Hernias are more common in elderly people owing to degenerative weakness of muscles and fibrous tissue. Inci sional hernias ar e more common after wound complications and in patients with a high body mass index; how ever, a major risk factor is the surgeon and the way the abdominal wall was closed.